/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.tomcat.util.http;

/**
 * Useful methods for Content-Type processing
 *
 * @author James Duncan Davidson [duncan@eng.sun.com]
 * @author James Todd [gonzo@eng.sun.com]
 * @author Jason Hunter [jch@eng.sun.com]
 * @author Harish Prabandham
 * @author costin@eng.sun.com
 */
public class ContentType {

	/**
	 * Parse the character encoding from the specified content type header.
	 * If the content type is null, or there is no explicit character encoding,
	 * <code>null</code> is returned.
	 *
	 * @param contentType a content type header
	 */
	public static String getCharsetFromContentType(String contentType) {

		if (contentType == null) {
			return (null);
		}
		int start = contentType.indexOf("charset=");
		if (start < 0) {
			return (null);
		}
		String encoding = contentType.substring(start + 8);
		int end = encoding.indexOf(';');
		if (end >= 0) {
			encoding = encoding.substring(0, end);
		}
		encoding = encoding.trim();
		if ((encoding.length() > 2) && (encoding.startsWith("\""))
				&& (encoding.endsWith("\""))) {
			encoding = encoding.substring(1, encoding.length() - 1);
		}
		return (encoding.trim());

	}

	/**
	 * Returns true if the given content type contains a charset component,
	 * false otherwise.
	 *
	 * @param type Content type
	 * @return true if the given content type contains a charset component,
	 * false otherwise
	 */
	public static boolean hasCharset(String type) {

		boolean hasCharset = false;

		int len = type.length();
		int index = type.indexOf(';');
		while (index != -1) {
			index++;
			while (index < len && Character.isSpace(type.charAt(index))) {
				index++;
			}
			if (index + 8 < len
					&& type.charAt(index) == 'c'
					&& type.charAt(index + 1) == 'h'
					&& type.charAt(index + 2) == 'a'
					&& type.charAt(index + 3) == 'r'
					&& type.charAt(index + 4) == 's'
					&& type.charAt(index + 5) == 'e'
					&& type.charAt(index + 6) == 't'
					&& type.charAt(index + 7) == '=') {
				hasCharset = true;
				break;
			}
			index = type.indexOf(';', index);
		}

		return hasCharset;
	}

}
